I have a sole proprietorship in Canada and I offer my services to former employer down in US. I am a Mechanical Design Engineer. This was done so that I can continue working for them while I am residing in Canada. I have all sorts of proof about my job, letter of employment from reporting manager on hours, NOC A duties, credibility. I have tax documents, I have invoices, and I have proof of ownership of my sole prop. Can I use my last three invoices to able to extend my spouse's SOWP?